In integrated circuits, the performance of P-type Metal-Oxide-Semiconductor (PMOS) devices and N-type Metal-Oxide-Semiconductor (NMOS) devices often need to be modulated to suit to the customized requirements of different circuits. For example, some circuits may prefer the PMOS and the NMOS devices therein to have different saturation currents than the PMOS and the NMOS devices in other circuits.
In existing circuits, the modulation of the PMOS and NMOS devices were achieved by adjusting the gate sizes of the PMOS or NMOS devices. However, since the gates of the PMOS devices and NMOS devices in a local region (such as a core region and an Input/output (IO) region) were formed simultaneously, the gates of the PMOS devices and NMOS devices in the local region have a same size. The adjustment in the PMOS devices thus also adversely affects the performance of the NMOS devices, and vice versa.